As discussed in What is the data output coding format used in AD7124-4/AD7124-8? the ADCs operate in unipolar or bipolar coding modes.
When unipolar mode is selected the ADC output code for any analog input voltage applied to the analog inputs can be calculated using the following formula as:
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Code = (2^N × AIN x Gain)/VREF |
· where AIN is the applied differential input voltage · VREF is the reference applied to the ADC. · N = 24 (number of data output bits) · Gain is the PGA settings |
Example: AIN = 1V, VREF=2.5V, PGA = 1. The equivalent code in unipolar mode is
Code = (2^N × AIN xGain)/VREF = (2^24 x 1V x 1)/2.5V = 6710886
When bipolar mode is selected the ADC output code for any analog input voltage applied to the analog inputs can be calculated using the following formula as:
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Code = 2^ (N – 1) × [(AIN x Gain/VREF) + 1]
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· where AIN is the applied differential input voltage · VREF is the reference applied to the ADC. · N = 24 (number of data output bits) · Gain is the PGA settings |
Example: AIN = 1V, VREF=2.5V, PGA=1. The equivalent code in bipolar mode is
Code = 2^ (N – 1) × [(AIN/VREF) + 1] = 2^ (24 – 1) × [(1V x 1/2.5V) + 1] = 11744051